Composite set



Aug. 21, 1928. 1,681,216

D. E. BRANSON ET AL COMPOSITE SET Filed Feb. 26, 1927 1 Zine Circuit Patented Aug. 21, 1928.

UNITED, STATES 1,681,216 PATENT OFFIc DAVID E. BRANSON; or :sroomrrntngnnw JERSEY, Ann ROY B. SHANCK, or FLUSH- me, NEW YORK, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH coir- PANY, A CORPORATION oF'NEw YORK. I

} comrosrrn smu a ipncaaon filed February 26, 1927. Serial No. 171,219.

This invention relates to multiplex signalmg systems and more particularly to improvements in arrangements, such as composite sets, usually associated with the terminal facilities of the lines of such systems to prevent the different currents utilized from interfering with each other.

In" a signaling system in which bothtelephone and telegraph currents are transmitted over the line circuits thereof it has been the practice to associatewith Y the .terminalfacilities of such line circuits a device known as a composite. set whereby the incoming telegraph: and telephone currents may be separated and divertedto their re spective circuits without interference with each other. The composite set, furthermore, functions to preventthe outgoing telegraph currents from entering the "telephone a path at the terminal facilities and vice versa. It isone of the primary objects of the composite set of this invention to provide a novel means for preventing the telegraph currents originating at the terminal of the line from entering the telephone circuits, or

V phantom circuits, thereat :and thereby tobviating the disturbances caused thereby,

which disturbances are commonly called telegraph thump. The'compositejsetcof the, invention makes use of the balanceprinciple to minimizethejamount of' telegraph cur rent which may get into the telephone circuits. This involves the use of auxiliary neutralizing or balancing circuits connected to each telegraph leg and to the transformer Winding of the telephone circuit to neutralize in said transformer any telegraph current transmittedthereto. Further objects and features of the invention will appear more fullyfrom the detailed description thereof hereinafter given.

The invention may; be more fully, under-1 stood-from the following description together with the accompanying drawing in the Figures 1, 2, and: 30f which tlie invention is illustrated Fig, lrrshows: azcircuit diagram' embodying a preferred form of the invention. Fig, 2 shows a schematic arrangement Which is the equivalent of Fig.

1. In Fig: 3 theparrangements of the invention are shown asa'ppliedto a system utilizing a phantom-telephoneline Like ref erence characters have been utilised to de note like parts in all of thefigures of the lnvention.

In Fig; l is shown a line circuitwvhi'ch coming inover the line from entering the telephone cn'cuit. Brldgedacross the-conductors ofthe llne clrcuit is a tetegraph L and the condensers G and C This would be provided condensers,fsuch as C andC to prevent the telegraph currents branch comprising the inductances L and arrangement of 'inductanc'esand capacities would tend to prevent the telephonecurrents from entering the telegraph branch; Connected to this bridge would be the t'ele-g;

graph legs 1 and 2 leading to the usual send- .ing apparatus comprising batteries and switching means; The above described arrangements comprise: t substantially y a cornpositeset of'the priorart. In accordance,

each ofthe telegraph legs 1 and 2, respectively the, auxiliary balancing circuits 3 and 4. Circuit 3 includes an inductance L and a capacity (l andis connected to the oppo with this invention therefisconnected to whenvoltages are applied to either or both :willbe set up by these auxiliary circuits 3 and at in the coilL inlsuch a way that with of the telegraph legs, which voltages mightj be setup in coil. L ;v neutralizing voltages thegproper constants for each of: thec ele iiig of condensersC; and 0;; and resistances "R R and R is connected to thejneutralizing-circuits 3-and 4' so as to give thesame admittance between the two neutralizing circuits and also to groundthat is given by the line circuit itself. The condensers C inentslittle'or nointer-ference or thumb current will result. and the-telephone circuit will not beaffected. A networlg 'jconsist and G are apart of; this network for preventing ny unnecessary current flow from thegtelegraph battery, I

a The method of neutralization at @537 interfering telegraph currents mayf i be more clearly "understood from the arrangements of Fig. 2. which shows the circuit arrangement of Fig 1 drawn up in slightly different form to show the bridged arrangement between the telegraph transmitter branch and the telephone drop circuit. If the impedances of the 'arious ljn'idgc elcmcuts are given, the proper values of the network consisting of condensers C, and C and resistances 11,. R, and R may be omitted. The two conditions when this may be done and at which time a close balance of the bridge is obtained are whcn:

(l) Impedances of coils L L L and L are all equal and large. Impedances of condensers C C C and C, are allequal and small.

(2) Impedances of coils L L. L and L, are all equal and small. Impedances of condensers C,, C,. C and C, are all equal and large. Itis pointed out that in order to preserve the proper telephone frequency characteristic and to prevent the shunting effect of the telegraph bridge on the telephone circuit, condition (1), above, would be the more practicable.

Another condition exists similar to cases (1) and above, in which the balancing network may be omitted when the impedances of coils L L L, and L, are equal and small and the impedances of condensers (1,, C C and C are equal and small. For this condition, the line impedance will be large in comparison to the impedances of the individualparts of the bridge and the balance will not be materially alTccted by the connection to the line. For this condition, the telegraph transmitter branch will shunt to some extent the tel'ephonebranch and the telephone branch will also shunt to some effect the telegraph branch.

In Fig. 3, the arrangements of the invention are. shown as applied for the purpose of neutralizing interference or telegraph thump in a system including a phantom telephone circuit. Two line circuits I and II are illustrated connected to the telephone lines I and II. Line circuit I and its associated apparatus is identical with the arrangements shown in F ig. 1, like reference characters being used to denote like parts. Line circuit II is identical with line circuit I, like reference characters with the added designation prime being used to denote like parts. Connected between the midpoints of coils L and L is a circuit including the coil L which is one of the windings of a transformer to which the phantom circuit is connected. Bridged across the conductors 3 and 4 associated with line circuit I is a phantom neutralizing circuit 5, 6. A connection is made from this circuit to the side of the phantom coil L opposite to that which is connected to line circuit I. Coil L and condenser C have the same impedance characteristics as the combined effect of coils L and L and condensers C and C the coil L being of little eflect since its Coils are connected parallel opposed as far as the phantom circuit is concerned. Also coil L, and condenser C have the same impedance characteristics as the combined cil'cct of coils L and L, and condensers C, and C In case it'becomcs necessary to add the balancing network to the phantom neutralizing circuit similar to that described for the side circuit, the bridged network consisting of condensers C and C and resistances it,, I and It may be connected across this neutralizing circuit as shown. \Vith such an arrangement any disturbing voltages set up in coil'L, by telegraph currents from the set; of line I would be neutralized by opposing voltages set up in said coil by the neutralizing circuit 5, 6; Associated with the line circuit II is a similar phantom neutralizing circuit 5. 6'. This circuit is connected to the sideof phantom coil L opposite to that connected to coil L,,. In a. manner similar to that heretofore described interfering,voltages from telegraph currents from the set of line II set up in coil L, will be neutralized by opposing voltages set up in said coilby the operation of circuit 5', (3'.

The method of neutralization, as illus trated by this invention, may be applied to any type of battery, arrangements for the various telegraph systems since it makes no difference whether the circuits operate on a ground return or as a metallic circuit. This would apply to both the metallic telegraph system whether single or full commutation and a duplex system having a ground return. Accordingly, while the invention has been disclosed as embodied in certain specific arrangements which are deemed desirable, it is understood that it is capable of: embodiment in many and other widely varied forms without departing from the spirit. of the invention as defined by the appended claims.

.lVhat is claimed is:

1. A transmission line. a connectingmeans serially included in said line. a telephone circuit associated with said line through said connecting means, a composite set including a telegraph bridge across said line circuit. telegraph legs associated with each side of said line circuit through said bridge. and auxiliary balancing circuits connecting each of said telegraph legs to sides of said connecting means opposite to those to which said telegraph legs are connected through said bridge.

2. A transmission line. aconnecting means included, serially therein, a telegraph circuit connected to one of the sides of said line, and an auxiliary balancing circuit connecting said telegraph circuit to a side of said connecting means opposite to that connected to said side of said line to which said telegraph circuit is connected.

3'. A transmission line, a winding included serially therein, telegra h circuits connected to each of the sides 0 said line, auxiliary balancing circuits connecting each of said telegraph circuits to sides of said winding opposite to those to which each telegraph circuit is connected, and a balancing network connected across said auxiliary balancing circuits,

4. A transmission line, a coil included serially therein, telegraph circuits connected to each of the sides of said line, auxiliary balancing circuits connecting each of said telegraph circuits to sides of said coil opposite to those to which each telegraph circuit is connected, a second transmission line having the same elements in combination as said first mentioned line, a circuit including a phantom coil and being connected to the midpoints of the coils serially included in each of said transmission lines, a phantom balcuit bridged across the auxiliary balancing circuits associated with said second trans- IDISSIOD line and means to connect each of said phantom balancing circuits with sides of said phantom coil opposite to those connected to the lines each of said phantom balancing circuits are associated with.

In testimony whereof, we have signed our names to this specification this 24th day of February, 1927. y

DAVID EQBRANSON. ROY B. SHANCK. 

